Development and reproduction of Bemisia tabaci （Homoptera： Aleyrodidae） on three bean species

Abstract The development, survivorship and reproduction of Bemisia tabaci B-biotype on three bean species were studied at 26±1°C in the laboratory. The developmental periods from egg to adult varied from 27.80 days on garden beans to 18.20 days on soybeans. The survivorship from egg to adult on soybeans, cowpeas and garden beans was 77.14, 70.14 and 64.28%, respectively. The average longevity of female adults ranged from 12.30 days on soybeans to 9.80 days on garden beans, and the oviposition of B. tabaci varied from 160.85 eggs on soybeans to 98.00 eggs on garden beans. Life table parameters were calculated as biological attributes for Bemisia tabaci populations fed on three bean species. The results indicated that the intrinsic rate of increase (r_m), the finite rate of increase (λ) and net reproductive rate (R₀) were high for populations fed on soybeans, with values of 0.1857, 1.2041 and 82.1576, respectively. The corresponding values were less for populations fed on garden beans, with values of 0.1097, 1.1159 and 31.2661, respectively. The parametric values for cowpeas were intermediate between soybeans and garden beans but no significant difference were observed for the r_m values for soybeans and cowpeas. Experimental evidence in our investigation indicated that Bemisia tabaci is best adapted and shows the greatest preference for soybean of the three bean species tested in this study.     

Demonstration and preliminary characterization of α-amylase in the sweetpotato whitefly,Bemisia tabaci (Aleyrodidae: Homoptera)

An α-amylase that hydrolyzes unmodified starch or amylopectin azure was demonstrated in crude and partially purified extracts prepared from whole carcasses of sweetpotato whiteflies (SPW) (Bemisia tabaci Genn.).All nymphal instars and adult SPW, including newly eclosed crawlers that had not yet fed on plant materials, were found to have active α-amylase. α-Amylase activity per mg protein was greatest in 1st instars and decreased with age up to the “pupal” stage, with a very slight increase in activity in adults. However, activity per individual did not differ substantially as a function of age.The α-amylase had an apparent molecular weight of about 70 kDa, an isoelectric point of 6.32 and eluted with about 250 mM NaCl from a strongly basic anion-exchange column.The enzyme activity was inhibited by EDTA and not activated by either NaCl or KNO₃. CaCl₂ strongly enhanced activity.α-Amylase activity was greatest at pH 7.0, but there was considerable activity at pHs above 7.0.The K_m of the α-amylase was 1.47 Mm with p-nitrophenyl α-d-malto-heptaoside as substrate.The presence of an amylolytic enzyme in a phloem-feeding insect is unexpected and raises questions about current assumptions of feeding behavior of this species.     

Development and reproduction of ‘B＇ biotype Bemisia tabaci （Gennadius） （Homoptera： Aleyrodidae） on four ornamentals

Abstract Effects of four commercial ornamentals on the development, survivorship and reproduction of the whitefly B biotype Bemisia tabaci (Gennadius) were studied in the laboratory (temperature 26 ± 1 °C; relative humidity 75%–90%; L: D 14:10). The total survivorship from egg to adult on hibiscus ( Hibiscus rosa-sinensis L.), poinsettia ( Euphorbia pulcherrima Will), cottonrose hibiscus ( Hibiscus mutabilis L.) and variegated leafcroton ( Codiaeum variegatum'Aucubaefolium' ) were 33.69%, 40.55%, 79.11%, and 29.39%, respectively. The developmental periods from egg to adult varied from 23.12 days on cottonrose hibiscus to 32.13 days on hibiscus. The average longevity of adult females ranged from 6.87 days on variegated leafcroton to 21.07 days on poinsettia. The average numbers of eggs laid per female were 9.20, 25.13, 54.45, and 26.79 on the above respective hosts. The intrinsic rates of natural increase ( r_m ) for B biotype B. tabaci on cottonrose hibiscus was the highest. Based on life table analyses of whitefly populations, cottonrose hibiscus was the most suitable host for B biotype B. tabaci in this study.     

Survie de Bemisia tabaci (Homoptera: Aleyrodidae) aux conditions hivernales de la zone nord méditerranée

L’objectif de ce travail est d’étudier l’influence des températures hivernales sur la survie des B. tabaci adultes. Les individus sont soumis à un cycle de températures qui correspond aux températures observées pendant les 24 heures d’une des journées les plus froides de l’hiver du sud de la France (Perpignan). L’évolution de ces températures est reproduite en conditions contrôlées, et les individus sont exposés à un, trois ou quatre de ces cycles. Après un cycle de 24 heures, le taux de survie moyen des individus est de 73,5% alors que celui du lot témoin est de 85%. Après une exposition à 3 cycles, le taux moyen de survie reste encore relativement élevé (44,4%). Les chances de survivre à 4 cycles de 24 heures est de 7,4%. Le Nord méditerranéen semble être une zone tampon pour le maintien en extérieur des populations de B. tabaci car ni les températures minimales régulièrement enregistrées, ni leur durée, ne sont clairement limitantes.     

Population fluctuation and persistence of one-host–two-parasitoid systems depending on resource distribution: from parasitizing behavior to population dynamics

Population dynamics and variability were examined in one-host–two-parasitoid experimental systems with different resource distributions: resource-clumped and resource-sparse conditions. The system consists of a seed beetle host, Callosobruchus chinensis, and two parasitoid wasps, Anisopteromalus calandrae (Pteromalidae) and Heterospilus prosopidis (Braconidae). In the resource-clumped condition, suitable hosts for parasitism (the late fourth-instar larvae and pupae) were clumped in 1 large resource patch, but they were scattered evenly among 16 small patches in the resource-sparse condition. Population censuses were conducted at 10-day intervals in long-term cultures, renewing 10 g of azuki beans (Vigna angularis). In both resource conditions, the first period was a single-species system of C. chinensis only, and A. calandrae was added in the second period. The one-host–one-parasitoid system with C. chinensis and A. calandrae showed stable population dynamics with small fluctuations. After addition of H. prosopidis in the third period, two of three replicates persisted to day 800 in each resource condition, although one replicate in each went to extinction at an immediate outbreak of the H. prosopidis population after the introduction. Population variabilities of C. chinensis and H. prosopidis were significantly higher and the mean population size of A. calandrae was significantly smaller in the resource-sparse condition than that in the resource-clumped one. A short-term experiment on parasitism efficiencies revealed that H. prosopidis parasitized significantly more at a low host density in the resource-sparse condition than in the resource-clumped one. Mutual interference of H. prosopidis was weak enough at low parasitoid densities but became abruptly stronger with high densities. Providing fresh hosts in a mixture of already parasitized ones, host-searching behaviors of a parasitoid were recorded by video for 3 h and were compared between the two wasp species. H. prosopidis could parasitize fresh hosts more efficiently than A. calandrae through frequent long-distance walks (walking to distant beans at one bout or outside a clump of beans with hosts and back soon on a distant bean of the clump) after reencounters with parasitized hosts. Considering all the experimental results, populations were judged to be more fragile and more likely to go to extinction in the resource-sparse condition than in the resource-clumped one. A higher attacking efficiency of H. prosopidis destabilized population dynamics more in the resource-sparse condition. Received: December 23, 1998 / Accepted: January 20, 1999     

Population dynamics of Stenoma catenifer Walsingham (Lepidoptera: Depressariidae) on Hass avocado orchards in México

Avocado production in Mexico represents an income of more than $3.2 billion dollars per year in foreign exchange. Unfortunately, several factors can limit the export of this fruit. One of such limiting factor is the avocado seed moth, Stenoma catenifer; however, its population dynamics is barely known. Therefore, is relevant to study the environmental factors affecting population changes, aimed to improve its management. In this study, we monitored the population fluctuations of S. catenifer males and explored its relationship with temperature and relative humidity by using pheromone-baited traps in Hass avocado orchards in the state of Colima, Mexico. From June 2018 to June 2019, a total of 6,836 males of the avocado seed moth were collected, with two population peaks. The first in June-August, during the fruiting stage, and the second in December-January, coinciding with the end of fruiting and flowering stages. Fruit infestation ranged from 0.0 to 65.0% in the orchards examined. Cluster analysis and principal coordinate analysis indicated that sampling time and relative humidity group together but differ from temperature. The effect of relative humidity and temperature on catches was analyzed by relating non-parametric bivariate distributions. The highest male catches were recorded at temperatures greater than 15.8 °C and relative humidity greater than 60% while low relative humidity did not favor moth catches. These results may be useful to predict bioecological conditions for the occurrence of populations of this pest.     

The uptake and penetration of pirimiphos-methyl into susceptible and resistant strains of the rust red flour beetle—Tribolium castaneum,herbst (coleoptera: tenebrionidae)

1. The uptake and penetration of ¹⁴C-labelled pirimiphos-methyl into two strains of T. castaneum are compared.2. Less radioactivity penetrated into the internal tissues of the resistant strain compared to the suceptible strain.3. The differences in uptake could not be accounted for by increased excretion of radiolabel by the resistant strain.     

Réaumur (1683–1757): the discoverer of parasitoids in France

Early French discoveries of insect parasitoids and various aspects of their life cycle are discussed in this paper. Parasitism in insects first attracted the attention of French scientists in the 18th century, despite indifference of the famous encyclopedists of “the Age of Enlightenment” to this group of animals. Fortunately, a distinguished scientist of many talents, R.A. Ferchault de Réaumur (1683–1757), was interested in the study of insects. His work on insects, “Mémoires pour servir à l’histoire des insectes” published in six volumes, remains his most well known opus. He was the first person in France to describe an entomophagous insect (probably a Cotesia species) as well as several aspects of the biological characteristics of parasitoid life in 1736. Together with Latreille (1762–1833), he may be considered one of the founding fathers of entomology in France.     

Dynamic changes in photosynthesis and chlorophyll fluorescence in Nicotiana tabacum infested by Bemisia tabaci (Middle East–Asia Minor 1) nymphs

Bemisia tabaci Middle East–Asia Minor 1 (MEAM1) is a worldwide pest. To determine whether MEAM1 nymphs produce the same symptoms in different host plants, we measured the plant growth and chlorophyll content of tobacco and cotton plants that were infested by MEAM1 nymphs. Furthermore, to investigate the spatial and temporal changes in photosynthesis caused by MEAM1 nymphs, the net photosynthetic rate (Pn) and chlorophyll a fluorescence of local and systemic tobacco leaves were assayed at 8, 11, 14, and 20 days after MEAM1 adult removal, which represent the stages of 1st, 2nd, 3rd, and 4th instar nymphs, respectively. The results showed that MEAM1 nymph infestation reduced the plant height and internode length of tobacco at 14 and 20 days, as well as the dry weight of infested and systemic tobacco leaves. However, MEAM1 nymph infestation did not affect the plant height or internode length of cotton. Also, the dry weight and chlorophyll and carotenoid content of infested and systemic leaves of cotton plants were not influenced by MEAM1 nymph infestation. However, the contents of chlorophyll a and b and carotenoids in infested tobacco leaves decreased over time; the chlorophyll a content of systemic tobacco leaves decreased at 11, 14, and 20 days. The chlorophyll and carotenoid contents in infested and systemic leaves of cotton plants were not influenced by MEAM1 nymph infestation. In addition, the Pn of infested tobacco leaves decreased at 14 and 20 days, while the Pn in systemic tobacco leaves decreased after 11 days. The greatest decrease in performance index on absorption basis (PI _ABS ) of infested and systemic tobacco leaves occurred on day 14. The fluorescence intensity at 2 ms (J peak) and 300 μs (K peak) increased on day 14, which indicates that 3rd instar nymphs caused serious damage to the primary photochemical reactions and donor side of PSII. These results suggest that MEAM1 nymph infestation had different effects on tobacco and cotton plants. The infestation caused spatial and temporal changes in photosynthesis in tobacco plants. The lower chlorophyll a content may have been related to the lower net photosynthetic rate of systemic and infested tobacco leaves. The decreased stability of the oxygen-evolving complex and the reaction center of PSII and the decrease in electron transport were the main reasons for the decrease in the level of photosynthesis in tobacco leaves caused by MEAM1 nymphs during various stages of infestation.     

Population dynamics and "outbreaks" of diamondback moth (Lepidoptera: Plutellidae) in Guangdong province, China: climate or failure of management?

Diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), became the major pest of Brassica vegetable production in Guangdong, a province in southeastern China, in the late 1980s and has continued to challenge growers, particularly during the spring and autumn. Control has relied on insecticides and, as has happened in other parts of the world, resistance to these has evolved and subsequent field control failures have occurred. We review and summarize the history of diamondback moth management in Guangdong. We show that the geographic distribution of the pest in China is well described by a simple climate niche model. Our model predicts the seasonal phenology and some of the variation in abundance among years in Guangdong. Discrepancies may reflect migration and insecticide use at a landscape level. The scale of the pest problem experienced varies with management practices. Local production breaks, and strict post harvest hygiene are associated with lower pest pressure on large-scale production units. As more and more insecticides become ineffective the need to implement an insecticide resistance management strategy, as well as basic integrated pest management practices, will become more pressing. The potential use and development of a better forecasting system for diamondback moth that will assist these developments is outlined.     

Biological Control ofBemisia argentifolii(Homoptera: Aleyrodidae) on Poinsettia with Inundative Releases ofEncarsia formosa(Hymenoptera: Aphelinidae): Are Higher Release Rates Necessarily Better?

The effectiveness of inundative releases of the parasitoidEncarsia formosafor control ofBemisia argentifoliion poinsettia was determined in replicated experimental greenhouses. We evaluated two release rates ofE. formosa:a low release rate (1 wasp/plant/week, released in two greenhouses, in spring 1995) and a high release rate (3 wasps/plant/week, released in two greenhouses, in fall 1993), each over a 14-week growing season. Each release trial had one or two control greenhouses in whichB. argentifoliideveloped on poinsettia in the absence ofE. formosa.Life-tables were constructed forB. argentifoliiin the presence and absence ofE. formosaby using a photographic technique to follow cohorts of whiteflies on poinsettia leaves. Weekly population counts of the whitefly were also made. In the absence ofE. formosa,egg to adult survivorship ofB. argentifoliion poinsettia was 75–81%. At the low release rate, egg to survivorship ofB. argentifoliiwas 5% and parasitism was 13%. At the high release rate, egg to adult survivorship forB. argentifoliiwas 8% and parasitism was 23%. The net reproductive rates (R₀) forB. argentifoliipopulations in the absence ofE. formosaranged from 18.01–26.12, indicating a rapidly increasing population. Net reproductive rates for whitefly populations subject to wasp releases were 1.54 for the low release rate greenhouses and 2.11 for the high release rate greenhouses, indicating substantially reducedB. argentifoliipopulation growth. The low release rate provided better control ofB. argentifoliithan the high release rate. This difference was attributed to higher levels of mortality of whiteflies at the low release rate in the first 5–6 weeks of the growing period. We suggest that mutual interference may also have affected observed levels of mortality and parasitism.     

Population genetic structure of two primary parasitoids of Spodoptera frugiperda (Lepidoptera), Chelonus insularis and Campoletis sonorensis (Hymenoptera): to what extent is the host plant important?

Plant chemistry can strongly influence interactions between herbivores and their natural enemies, either by providing volatile compounds that serve as foraging cues for parasitoids or predators, or by affecting the quality of herbivores as hosts or prey. Through these effects plants may influence parasitoid population genetic structure. We tested for a possible specialization on specific crop plants in Chelonus insularis and Campoletis sonorensis, two primary parasitoids of the fall armyworm, Spodoptera frugiperda. Throughout Mexico, S. frugiperda larvae were collected from their main host plants, maize and sorghum and parasitoids that emerged from the larvae were used for subsequent comparison by molecular analysis. Genetic variation at eight and 11 microsatellites were respectively assayed for C. insularis and C. sonorensis to examine isolation by distance, host plant and regional effects. Kinship analyses were also performed to assess female migration among host‐plants. The analyses showed considerable within population variation and revealed a significant regional effect. No effect of host plant on population structure of either of the two parasitoid species was found. Isolation by distance was observed at the individual level, but not at the population level. Kinship analyses revealed significantly more genetically related—or kin—individuals on the same plant species than on different plant species, suggesting that locally, mothers preferentially stay on the same plant species. Although the standard population genetics parameters showed no effect of plant species on population structure, the kinship analyses revealed that mothers exhibit plant species fidelity, which may speed up divergence if adaptation were to occur.     

Identification of genes differentially expressed during interaction of resistant and susceptible apple cultivars (Malus × domestica) with Erwinia amylovora

Background  

The necrogenic enterobacterium, Erwinia amylovora is the causal agent of the fire blight (FB) disease in many Rosaceaespecies, including apple and pear. During the infection process, the bacteria induce an oxidative stress response with kinetics similar to those induced in an incompatible bacteria-plant interaction. No resistance mechanism to E. amylovora in host plants has yet been characterized, recent work has identified some molecular events which occur in resistant and/or susceptible host interaction with E. amylovora: In order to understand the mechanisms that characterize responses to FB, differentially expressed genes were identified by cDNA-AFLP analysis in resistant and susceptible apple genotypes after inoculation with E. amylovora.     

Characterization of saponins and phenolic compounds: antioxidant activity and inhibitory effects on α-glucosidase in different varieties of colored quinoa (Chenopodium quinoa Willd)

ABSTRACT

This study investigated the contents of saponins and phenolic compounds in relation to their antioxidant activity and α-glucosidase inhibition activity of 7 colored quinoa varieties. The total saponin content was significantly different among 7 varieties and ranged from 7.51 to 12.12 mg OAE/g DW. Darker quinoa had a higher content of phenolic compounds, as well as higher flavonoids and antioxidant activity than that of light varieties. Nine individual phenolic compounds were detected in free and bound form, with gallic acid and ferulic acid representing the major compounds. The free and bound phenolic compounds (gallic acid and ferulic acid in particular) exhibited high linear correlation with their corresponding antioxidant values. In addition, the free phenolic extracts from colored quinoa exhibited higher inhibitory activity against α-glucosidase than the bound phenolic extracts. These findings imply that colored quinoa with abundant bioactive phytochemicals could be an important natural source for preparing functional food.     

Structural analysis and the effect of cyclo(His–Pro) dipeptide on neurotoxins—a dynamics and density functional theory study

The switching propensity and maximum probability of occurrence of the side chain imidazole group in the dipeptide cyclo(His–Pro) (CHP) were studied by applying molecular dynamics simulations and density functional theory. The atomistic behaviour of CHP with the neurotoxins glutamate (E) and paraquat (Pq) were also explored; E and Pq engage in hydrogen bond formation with the diketopiperazine (DKP) ring of the dipeptide, with which E shows a profound interaction, as confirmed further by NH and CO stretching vibrational frequencies. The effect of CHP was found to be greater on E than on Pq neurotoxin. A ring puckering study indicated a twist boat conformation for the six-membered DKP ring. Molecular electrostatic potential (MESP) mapping was also used to explore the hydrogen bond interactions prevailing between the neurotoxins and the DKP ring. The results of this study reveal that the DKP ring of the dipeptide CHP can be expected to play a significant role in reducing effects such as oxidative stress and cell death caused by neurotoxins.     

Fate of pathological prion (PrPsc92–138) in soil and water: prion-clay nanoparticle molecular dynamics

Pathogenic prion protein scrapie (PrP^sc) may contaminate soils for decades and remain in water in colloidal suspension, providing infection pathways for animals through the inhalation of ingested dust and soil particles, and drinking water. We used molecular dynamics simulations to understand the strong binding mechanism of this pathogenic peptide with clay mineral surfaces and compared our results to experimental works. We restricted our model to the moiety PrP(92–138), which is a portion of the whole PrP^sc molecule responsible for infectivity and modeled it using explicit solvating water molecules in contact with a pyrophyllite cleavage plane. Pyrophyllite is taken as a model for common soil clay, but it has no permanent structural charge. However, partial residual negative charges occur on the cleavage plane slab surface due to a slab charge unbalance. The charge is isotropic in 2D and it was balanced with K⁺ ions. After partially removing potassium ions, the peptide anchors to the clay surface via up to 10 hydrogen bonds, between protonated lysine or histidine residues and the oxygen atoms of the siloxane cavities. Our results provide insight to the mechanism responsible for the strong association between the PrP^sc peptide and clay nanoparticles and the associations present in contaminated soil and water which may lead to the infection of animals.     

Effect of Cigarette Smoking and Passive Smoking on Hearing Impairment: Data from a Population–Based Study

Objectives

In the present study, we aimed to determine the effect of both active and passive smoking on the prevalence of the hearing impairment and the hearing thresholds in different age groups through the analysis of data collected from the Korea National Health and Nutrition Examination Survey (KNHANES).

Study Design

Cross-sectional epidemiological study.

Methods

The KNHANES is an ongoing population study that started in 1998. We included a total of 12,935 participants aged ≥19 years in the KNHANES, from 2010 to 2012, in the present study. Pure-tone audiometric (PTA) testing was conducted and the frequencies tested were 0.5, 1, 2, 3, 4, and 6 kHz. Smoking status was categorized into three groups; current smoking group, passive smoking group and non-smoking group.

Results

In the current smoking group, the prevalence of speech-frequency bilateral hearing impairment was increased in ages of 40−69, and the rate of high frequency bilateral hearing impairment was elevated in ages of 30−79. When we investigated the impact of smoking on hearing thresholds, we found that the current smoking group had significantly increased hearing thresholds compared to the passive smoking group and non-smoking groups, across all ages in both speech-relevant and high frequencies. The passive smoking group did not have an elevated prevalence of either speech-frequency bilateral hearing impairment or high frequency bilateral hearing impairment, except in ages of 40s. However, the passive smoking group had higher hearing thresholds than the non-smoking group in the 30s and 40s age groups.

Conclusion

Current smoking was associated with hearing impairment in both speech-relevant frequency and high frequency across all ages. However, except in the ages of 40s, passive smoking was not related to hearing impairment in either speech-relevant or high frequencies.     

Small-scale field evaluation of the efficacy and residual effect of Fludora® Fusion (mixture of clothianidin and deltamethrin) against susceptible and resistant Anopheles gambiae populations from Benin,West Africa

The emergence of mosquitoes that can avoid indoor-deployed interventions, such as treated bed nets and indoor residual spraying, threatens the mainstay of malaria control in Zambia. Furthermore, the requirement for high coverage of these tools poses operational challenges. Spatial repellents are being assessed to supplement these vector control tools, but limitations exist in the residual effect of the repellent and the need for external power or heat for diffusion of the volatiles. A semi-field evaluation of a novel controlled release spatial repellent device (CRD) was conducted in Macha, Zambia. These devices emanate metofluthrin with no need for external power. Devices were deployed in huts within the semi-field system (SFS). Female Anopheles gambiae sensu stricto released within the SFS were trapped overnight by light traps and collected by aspiration the next morning inside and outside of huts to determine the extent of mosquito repellency and the impact on host-seeking and survival. Experiments studied the impact of number of devices as well as the presence of hut occupants. The study was complemented with numerical methods based on computational fluid dynamics to simulate spatial distribution of metofluthrin. Presence of CRDs was associated with significant reductions in indoor counts of mosquitoes, regardless of whether huts were occupied or not. Repellency ranged from 15 to 60% compared to huts with no devices. Reducing the number of devices from 16 to 4 had little impact on repellency. When huts were occupied, indoor mosquito host-seeking was higher in the presence of CRDs, whilst survival was significantly reduced. This study demonstrated that deployment of as few as four CRDs within a hut was associated with reduced indoor mosquito densities. As would be expected, presence of occupants within huts, resulted in greater indoor catches (both with and without devices). The increased indoor mosquito host-seeking and mortality in huts when devices were present may be explained by the excito-repellency activity of metofluthrin. These semi-field experiments provide preliminary data on the utility of CRD spatial repellents to reduce indoor densities of An. gambiae mosquitoes. Studies will further investigate the impact of CRDs on mosquito behaviour as well as epidemiological protective efficacy.